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U.S.C.G. Merchant Marine Exam

DDE – Unlimited HP

Q620 Motor Plants

(Sample Examination)

of 56 Q620 Motor Plants

8/18/2021

Q620 Motor Plants U.S.C.G. Merchant Marine Exam DDE-Unlimited HP Illustrations: 34

Choose the best answer to the following multiple choice questions.

1. You are assigned to a river push boat fitted with main propulsion diesel engines operating on the cycle represented in the polar timing diagram shown in the illustration. What combustion cycle event has a duration of 103o? Illustration MO-0206

o (A) Compression o (B) Intake • (C) Power o (D) Exhaust

If choice C is selected set score to 1.

2. When checking the cylinder jacket water cooling expansion tank level on a main propulsion diesel engine on your towing vessel while underway on a coast-wise voyage, what should be the expansion tank level?

• (A) The level should be in the upper part of the sight glass when the engine is at operating temperature.

o (B) The level should be out of sight high in the sight glass when the engine is at operating temperature.

o (C) The level should be in the lower part of the sight glass when the engine is at operating temperature.

o (D) The actual level is unimportant as long as it is visible in the sight glass when the engine is at operating temperature.

If choice A is selected set score to 1.

3. Before shutting down the main propulsion engines on a tractor tug, ideally what should be accomplished FIRST?

• (A) The engine should be operated with the load removed from the engine for several minutes, then shut down.

o (B) The engine should be operated at rated load for several minutes, then shut down. o (C) The engine should be shut down immediately with no delay period, regardless of the engine

load. o (D) The engine should be operated at a steady, but substantial load for several minutes, then

shut down.



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4. You are on a river towboat using main propulsion engines of the type shown in the illustration. What statement represents the procedure for inspection of the lower cylinder liner bore while in place inside the engine? Illustration MO-0227

o (A) With the particular piston positioned at BDC and the corresponding oil pan hand-hole cover removed, inspect the lower liner bore through the crankcase opening.

o (B) With the particular piston positioned at TDC and the corresponding air box hand-hole cover removed, inspect the lower liner bore through the crankcase opening.

o (C) With the particular piston positioned at BDC and the corresponding air box hand-hole cover removed, inspect the lower liner bore through the crankcase opening.

• (D) With the particular piston positioned at TDC and the corresponding oil pan hand-hole cover removed, inspect the lower liner bore through the crankcase opening.

If choice D is selected set score to 1.

5. You are analyzing the data used for trend analysis for a two-stroke main propulsion diesel engine on your river push boat. Although the engine has yet to experience a safety shutdown on high crankcase pressure, over time the crankcase pressure (which normally runs in a vacuum) has gradually become less negative. Which of the following failures would most likely be responsible for this condition?

o (A) Dribbling injector needle valve. • (B) Worn piston compression rings. o (C) Burned cylinder exhaust valve. o (D) Leaking crankcase handhole cover.

If choice B is selected set score to 1.

6. Prior to starting a diesel generator set engine fitted on your salvage tug, it has been determined that the transfer of make-up oil is required. At what checked level should you stop adding make-up oil?

o (A) When the oil level rises to a level well above the FULL mark on the dipstick. • (B) When the oil level rises to the FULL mark on the dipstick. o (C) When the oil level rises to the between the ADD and FULL marks on the dipstick. o (D) When the oil level rises to the ADD mark on the dipstick.



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7. You are about to check the valve lash adjustment on #1 cylinder's intake and exhaust valves of an auxiliary diesel engine fitted on the ship-docking tug to which you are assigned. You want to adjust the valve lash on both valves without having to reposition the crankshaft between adjustments. What should be the position of #1 piston to insure both the intake and exhaust valves are both in a position to facilitate valve adjustment?

o (A) The crankshaft should be barred in the direction of rotation with #1 piston at BDC having just completed an intake stroke.

• (B) The crankshaft should be barred in the direction of rotation with #1 piston at TDC having just completed a compression stroke.

o (C) The crankshaft should be barred in the direction of rotation with #1 piston at BDC having just completed a power stroke.

o (D) The crankshaft should be barred in the direction of rotation with #1 piston at TDC having just completed an exhaust stroke.


8. An engine that emits black smoke through the stack may indicate a misfiring cylinder. Assume that the auxiliary diesel engines on your articulated tug-barge unit have a fuel injection system that permits the injectors to be disabled for troubleshooting purposes by loosening the high pressure fuel injection line fitting at the injector nozzle while the engine is running and noting the response of the engine in terms emission of black smoke. Which of the following statements is true?

• (A) After disabling the injector of a given cylinder, if the engine previously producing black smoke now produces a clear stack, this indicates that the cylinder associated with the disabled injector is misfiring.

o (B) After disabling the injector of a given cylinder, if the engine previously producing black smoke continues to produce equally dense black smoke, this indicates that the cylinder associated with the disabled injector is misfiring.

o (C) After disabling the injector of a given cylinder, if the engine previously producing a clear exhaust now produces black smoke, this indicates that the cylinder associated with the disabled injector is misfiring.

o (D) After disabling the injector of a given cylinder, if the engine previously producing black smoke now produces even denser black smoke, this indicates that the cylinder associated with the disabled injector is misfiring.



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9. An auxiliary diesel engine on your towboat is equipped with an electric starting motor such as is shown in the illustration. For what reason is there a significant gap in distance between the start solenoid plunger (C) and the rod that is used to close the starter motor contacts. Illustration MO-0051

o (A) Upon starter solenoid coil energization, this gap delays the engagement of the pinion to the flywheel ring gear until after the starter motor contacts close.

• (B) Upon starter solenoid coil energization, this gap delays the closure of the starter motor contacts until after engagement of the pinion to the flywheel ring gear.

o (C) Upon starter solenoid coil energization, this gap compensates for starter motor armature reaction to minimize arcing at the brushes.

o (D) Upon starter solenoid coil energization, this gap prevents chattering and associated arcing of the starter motor contacts.


10. Various diesel engines onboard your salvage tug are started by means of either vane-type or air-turbine air-starting motors. At a minimum, in the absence of automatic drain valves, how often should moisture separators be drained of moisture while the vessel is underway?

o (A) Hourly • (B) Daily o (C) Weekly o (D) Monthly


11. The main engines on your harbor tug utilize a starting system with two air-start motors similar to that shown in the illustration. Upon pushing the start button, the solenoid air valve energizes open, but the air start relay valve fails to receive pilot air, and thus the starter motors and engine fail to rotate. Which of the listed conditions would most likely be the cause of the failure to start? Illustration MO-0200

o (A) The upper pinion fails to retract, which in turn does not allow the lower pinion to retract. Because retraction of both pinions is required to supply air to the air-start motors, the engine does not start.

o (B) The upper pinion fails to engage, which in turn does not allow the lower pinion to engage. Because engagement of both pinions is required to supply air to the air-start motors, the engine does not start.

o (C) The lower pinion fails to retract, which in turn does not allow the upper pinion to retract. Because retraction of both pinions is required to supply air to the air-start motors, the engine does not start.

• (D) The lower pinion fails to engage, which in turn does not allow the upper pinion to engage. Because engagement of both pinions is required to supply air to the air-start motors, the engine does not start.



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Q620 Motor Plants U.S.C.G. Merchant Marine Exam DDE-Unlimited HP Illustrations: 34 12. A diesel generator set on your ship-docking tug has a simplex lube oil strainer of the type shown in

the illustration, situated on the discharge side of the lube oil pump. At a specified engine rpm and lube oil temperature, you notice that the inlet pressure is increasing and the outlet pressure is decreasing, resulting in an unacceptable pressure drop. What should be done? Illustration MO-0057

• (A) While the engine is running, the cleaning handle (A) should be rotated one or more full turns to remove the accumulated dirt from the disk stack (C).

o (B) The drain plug (B) is removed to drain the sludge from the strainer sump, but the engine must be stopped to perform this operation.

o (C) While the engine is running, the drain plug (B) should be carefully loosened to drain the sludge from the strainer sump.

o (D) While the engine is running, the cleaning handle (A) should be rotated one-half turn to remove the accumulated dirt from the disk stack (C).


13. The tank-type full-flow lubricating oil filter is situated on the discharge side of the engine-driven lube oil pump on the main engines on your sea-going tug. Assuming oil pressure readings are observed at constant engine rpm and lube oil temperature, what is the indication of gradually clogging filter elements as long as the bypass relief valve remains closed?

o (A) The filter inlet AND outlet pressures BOTH gradually drop. o (B) The filter inlet pressure gradually drops, while the filter outlet pressure gradually rises. o (C) The filter inlet AND outlet pressures BOTH gradually rise. • (D) The filter inlet pressure gradually rises, while the filter outlet pressure gradually drops.


14. The diesel fuels burned in auxiliary and main diesel engines of tugboats operating in harbor areas are required to meet certain specifications. Among these are limits of certain contaminants to limit atmospheric emissions to acceptable levels. Which of the following soluble contaminants is applicable?

o (A) Asphaltenes • (B) Sulfur o (C) Total sediment o (D) Water



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15. The main engines on the harbor tug to which you are assigned are fitted with duplex secondary spin-on fuel filters. Concerning the selector handle, what statement is true?

o (A) The selector handle is placed in the "BOTH" position when the engine is running at low load or rpm. When the engine is running at high load or rpm, the selector handle is placed in either the "1" or "2" position depending upon which filter element is clean.

o (B) The selector handle is placed in the "BOTH" position when the engine is running at high load or rpm to accommodate higher fuel delivery requirements. When the engine is running at low load or rpm, the selector handle is placed in either the "1" or "2" position.

o (C) The selector handle is normally placed in the "BOTH" position regardless of the load or rpm on the engine in order to be able to double the fuel handling throughput at any load or rpm and allow the engine speed to be changed without worrying about the selector handle position.

• (D) The selector handle is placed in either position the "1" or "2" position regardless of the load or rpm on the engine. The selector handle is temporarily placed in the "BOTH" position only when transitioning from a restricted filter element over to a clean filter element.


16. The manufacturer of the diesel generator set drive engines used aboard your ship-docking tug recommends that no more than a 2 psig pressure drop across a fuel primary metal-edge suction strainer be allowed before recommended servicing. Assuming that the strainer inlet pressure is 4 psig, what would be the minimum allowable outlet pressure before recommended servicing?

• (A) 2 psig o (B) 2" Hg o (C) 6 psig o (D) 6" Hg


17. The river push boat to which you are assigned has diesel generators fitted with fuel injectors with the operating principle as shown in the illustration. In figure "B" which plunger rotation position corresponds to the engine running under no load at idle RPM? Illustration MO-0144

o (A) 1 • (B) 2 o (C) 3 o (D) 4



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18. The tractor tug to which you are assigned has diesel generators fitted with multi-plunger pumps with the metering principle as shown in the illustration. What statement is true concerning this injection pump type? Illustration MO-0145

o (A) As the load changes, the beginning of injection is constant, and the ending of injection is constant.

o (B) As the load changes, the beginning of injection is variable, and the ending of injection is constant.

o (C) As the load changes, the beginning of injection is variable, and the ending of injection is variable.

• (D) As the load changes, the beginning of injection is constant, and the ending of injection is variable.


19. The main propulsion diesel engines on your ship-docking tug are fitted with conventional hydraulically operated injector nozzles of the orifice type. When testing an injector by performing a pop-test on an injector test stand, you observe no leakage prior to reaching the popping pressure, the pressure holds at just below the popping pressure, the actual popping pressure is within specification, but the spray pattern is distorted. What maintenance is required?

o (A) The injector spindle and nozzle holder bore must be reconditioned or replaced. o (B) The injector needle valve and seat must be reconditioned or replaced. o (C) The injector spring compression must be readjusted or a broken spring replaced. • (D) The injector nozzle tip orifices must be reconditioned by cleaning or the tip replaced.


20. You suspect that a diesel generator set on your river push boat has a misfiring cylinder because the engine, although warm, is running roughly. The six-cylinder engine is fitted with a multi-plunger in-line high pressure fuel injection pump with hydraulically operated injector nozzles. When you slacken the high pressure fuel line fitting at No. 5 fuel injector nozzle, the engine continues to run roughly as before with no real change. Upon re-tightening the high pressure fuel line fitting, the engine begins and continues to run smoothly. What does this indicate?

o (A) No. 5 cylinder was and continues to be misfiring. You have successfully located the misfiring cylinder.

o (B) No. 5 cylinder was and continues to be firing properly. No. 1, No. 2, No. 3, or No. 4 cylinder is misfiring. No. 6 cylinder is firing properly.

o (C) No. 5 cylinder was and continues to be firing properly. No. 6 cylinder is misfiring. No. 1, No. 2, No. 3, and No. 4 cylinders are all firing properly.

• (D) No. 5 cylinder had been misfiring. You have successfully purged the air from the No. 5 cylinder high pressure fuel line, and the engine is no longer misfiring.



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Q620 Motor Plants U.S.C.G. Merchant Marine Exam DDE-Unlimited HP Illustrations: 34 21. The towboat to which you are assigned has main diesel engines fitted with intake and exhaust

systems as shown in the simplified illustration. What is the primary purpose of the intercooler? Illustration MO-0180

• (A) Increase the charge air density to increase the engine power output. o (B) Provide cooling to the turbocharger turbine. o (C) Provide cooling to the turbocharger blower. o (D) Eliminate the need for water jacketing of the exhaust receiver.


22. The diesel generator set drive engines on your river push boat are protected with heavy-duty oil bath air cleaners. The oil within these air cleaners should be periodically replaced in accordance with manufacturer recommendations. What statement best describes when it would be appropriate to deviate from the recommended frequency?

o (A) Replace the oil less frequently when the engine is exposed to dusty conditions (such as arc welding in the engine room), and replace the oil more frequently when the oil is unusually dirty or when it thickens.

o (B) Replace the oil more frequently when the engine is exposed to dusty conditions (such as arc welding in the engine room), and replace the oil less frequently when the oil is unusually dirty or when it thickens.

• (C) Replace the oil more frequently when the engine is exposed to dusty conditions (such as arc welding in the engine room), and replace the oil more frequently when the oil is unusually dirty or when it thickens.

o (D) Replace the oil less frequently when the engine is exposed to dusty conditions (such as arc welding in the engine room), and replace the oil less frequently when the oil is unusually dirty or when it thickens.


23. The diesel engines on your tug are all protected with dry-type air filters. When changing filter elements what visual indication would cause you to suspect that the engine has been contaminated with dust as the result of improperly sealing of the filter element gasket?

o (A) The "dirty" side of the air filter element is coated with dust. o (B) The "dirty" side of the air filter housing is coated with dust. o (C) The "clean" side of the air filter element is clean and free of dust. • (D) The "clean" side of the air filter element is streaked with dust.



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24. The salvage tug to which you are assigned has main engines fitted with intake and exhaust systems as shown in the illustration. Assume that the typical cylinder exhaust temperature at 75% of maximum, continuous rated load is between 850o and 900 o F. What will happen to the typical cylinder exhaust temperature when the load is increased to 100% of maximum continuous rated load? Illustration MO-0076

• (A) The temperature will increase. o (B) The temperature will not change. o (C) The temperature will decrease. o (D) The temperature will change, but in either direction.


25. Assuming the use of ultra-low sulfur content diesel fuel, what combination of conditions associated with harbor tug engine room operations would require the most frequent draining of exhaust systems of condensation?

o (A) Summer operations with prolonged idling on station. o (B) Winter operations with lengthy ship escort transit times. • (C) Winter operations with prolonged idling on station. o (D) Summer operations with lengthy ship escort transit times.


26. A main propulsion diesel engine on your towing vessel produces gray to black smoke under virtually all load conditions as observed at the stack. The heavier the load on the engine, the darker the smoke becomes. What condition would most likely account for this?

o (A) Leaking exhaust manifold cooling water jackets. o (B) Excessively worn exhaust valve guides. o (C) Leaking exhaust piping expansion joints. • (D) Excessively restricted exhaust silencer/muffler.


27. Your salvage tug is fitted with cooling water systems serving the main propulsion diesel engines as shown in the illustration. Which heat exchanger/cooler application and aspect would most likely require periodic mechanical cleaning with a specially designed brush? Illustration MO-0137

o (A) The outside of the tubes of the RW/FW heat exchanger. • (B) The inside of the tubes of the RW/FW heat exchanger. o (C) The outside of the tubes of the lube oil cooler. o (D) The inside of the tubes of the lube oil cooler.



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Q620 Motor Plants U.S.C.G. Merchant Marine Exam DDE-Unlimited HP Illustrations: 34 28. The fresh water cooling systems serving the main engines on your harbor tug are arranged as

shown in the illustration. If the fresh water thermostatic control valve fails in the position where 100% of the flow from flange "A" is permanently ported to flange "B" and flange "C" is permanently blocked, while starting and warming the engine with no load, what would be the resulting warm up time period? Illustration MO-0137

o (A) With no load, it is not possible to describe the time frame required to warm up the engine. • (B) With no load, the engine would require a relatively normal time frame to warm up. o (C) With no load, the engine would require a much longer than normal time frame to warm up. o (D) With no load, the engine would require a much shorter than normal time frame to warm up.


29. In comparison to a naturally aspirated 4-stroke cycle engine, what characteristics are associated with turbocharging?

• (A) The exhaust gas pressure on the engine exhaust manifold is increased, and the intake air temperature to the cylinders is increased.

o (B) The exhaust gas pressure on the engine exhaust manifold is decreased, and the intake air temperature to the cylinders is decreased.

o (C) The exhaust gas pressure on the engine exhaust manifold is decreased, and the intake air temperature to the cylinders is increased.

o (D) The exhaust gas pressure on the engine exhaust manifold is increased, and the intake air temperature to the cylinders is decreased.


30. The two-stroke cycle main propulsion engines on the river pushboat to which you are assigned are fitted with Roots-type blowers for scavenging purposes. Upon inspection of the air boxes, what condition would indicate a need to replace the Roots-type blower immediately?

o (A) Oil accumulations o (B) Iron dust residue o (C) Water accumulations • (D) Aluminum dust residue


31. A Roots-blown, two-stroke cycle main propulsion engine on the ship-docking tug to which you are assigned is emitting excessive bluish-tinged smoke from the stack. Further investigation reveals excessive lube oil consumption. What condition would most likely account for this?

• (A) Worn blower rotor shaft seals. o (B) Restricted scavenging air intake ports. o (C) Leaking fuel injector needle valve. o (D) Restricted blower air intake filter.



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Q620 Motor Plants U.S.C.G. Merchant Marine Exam DDE-Unlimited HP Illustrations: 34 32. The lubricating oil system supporting the main propulsion reduction gear on the ship-docking tug to

which you are assigned is fitted with a lube oil strainer as shown in the illustration. What strainer attribute will dictate the degree of filtration in terms of the particle size capable of being filtered? Illustration MO-0057

o (A) The number of discs in the disc-stack making up the straining element. o (B) The length of the oil sump enclosing the straining element. • (C) Vertical spacing between the metal discs as determined by the thickness of the cleaner

blades. o (D) The dimensions of the triangular oil passages in each disc conveying the strained oil upward.


33. The escort tug to which you are assigned is fitted with hydraulic clutches similar to that shown in the illustration. If the time required for the clutch to disengage is unacceptably long, which of the following conditions would most likely be responsible for this? Illustration MO-0089

• (A) Solid contaminants are present in the hydraulic fluid. o (B) Clutch operating fluid is maintained at too low a temperature. o (C) Clutch operating fluid is maintained at too high a temperature. o (D) Fluid clutch sump level maintained at too high a level.


34. The main engines on your articulated tug-barge unit are equipped with over speed trip devices as shown in the illustration. What statement concerning the operation of the over speed trip is true? Illustration MO-0171

• (A) The overspeed trip senses centrifugal force proportional to engine speed and shuts the engine down at a pre-determined, specified maximum speed setting.

o (B) The overspeed trip senses centrifugal force proportional to engine speed and limits the engine speed to the rated speed, while allowing the engine to continue to run at the rated speed.

o (C) The overspeed trip senses oil pressure proportional to engine speed and shuts the engine down at a pre-determined, specified maximum speed setting.

o (D) The overspeed trip senses oil pressure proportional to engine speed and limits the engine speed to the rated speed, while allowing the engine to continue to run at the rated speed.



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35. The main engines on your harbor tug are protected with a low crankcase oil level detector protective device designed to provide an alarm when the main sump oil level drops below a certain level. It is malfunctioning, and upon investigation you determine from the technical manual that the oil level detector is a sealed unit. What statement best represents the best strategy to remedy this situation?

• (A) The oil level detector must be replaced with a new detector if it is found to be defective, since field adjustments are not possible on this type of unit.

o (B) The oil level detector is adjusted just as if it was an unsealed unit, without regard to any seals associated with the unit.

o (C) The oil level detector seals must be broken before adjustments can be made, as long as new seals are established before placing the unit back into operation.

o (D) The oil level detector is adjusted just as if it was an unsealed unit, but the seals must be re-established before placing the unit back into operation.


36. The rated speed of the main propulsion diesel engines on your towing vessel is 900 rpm. The installed centrifugal over speed trip device similar to the one shown in the illustration is designed to shut down the engine at 110% of rated speed. Upon testing the over speed trip device, you determine that the actual shutdown occurs at 945 rpm. Which of the following would account for this? Illustration MO-0101

o (A) The throw-out weight (item 10) link bolt (item 15 and 16) is binding within the spring guide (item 14) drilling.

o (B) The compression spring (item 12) was excessively compressed when the over speed trip was last set.

o (C) The throw-out weight (item 10) pivot bolt (not labelled) is binding within the counterweight (item 1 through 9) drilling.

• (D) The jam nut was not properly tightened against the adjusting nut (items 13) when the over speed trip was last set.


37. The auxiliary oil-fired water-tube steam boiler on your ship-docking tug is equipped with a water column similar to that shown in the illustration. Assuming that the water level is at the normal operating water level (NOWL) of the boiler, what would be the result of alternately opening and reclosing each of the water column tri-cocks? Illustration MO-0093

o (A) Steam should issue from the uppermost tri-cock, and water should issue from both the middle and lowermost tri-cocks.

o (B) Steam should issue from both the uppermost and middle tri-cocks, and water should issue from the lowermost tri-cock.

• (C) Steam should issue from the uppermost tri-cock, and water should issue from lowermost tri-cock. Either steam or water could issue from the middle tri-cock.

o (D) Water should issue from each of the uppermost, middle, and lowermost tri-cocks.



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Q620 Motor Plants U.S.C.G. Merchant Marine Exam DDE-Unlimited HP Illustrations: 34 38. What would be the most practical and efficient way of removing soot deposits from the fire-sides of

the tubes of an auxiliary water-tube natural-circulation boiler as fitted on your sea-going tug?

• (A) Use of an air lance. o (B) Use of a high-pressure water jet. o (C) Use of a power driven wire brush. o (D) Use of a suitable acid.


39. You are observing the flame condition on an oil-fired auxiliary boiler installed on your coast-wise tug through an observation window peephole. The flame is a reddish color accompanied by a noticeably panting/pulsating furnace. What would be the correlating color of the gases exhausting from the stack under these conditions?

o (A) White smoke. • (B) Dense black smoke. o (C) Light brown haze. o (D) Clear stack.


40. Due to environmental and safety concerns, the towing winch drive diesel engine cooling water system is treated with propylene glycol for protection against freezing. According to the illustration, what would be the limit of protection if 40 pints of propylene glycol are used in treating a cooling water system with a volumetric capacity of 10 gallons? Illustration MO-0209

o (A) 10oF o (B) -6oF • (C) -30oF o (D) -53oF


41. In a closed, re-circulating fresh water cooling system used for the diesel generators on your coastwise towing vessel, what function would chemical treatment with organic phosphates primarily perform?

o (A) Corrosion inhibition. • (B) Scale control and suppression. o (C) Biological growth inhibition. o (D) Freezing point depression.



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Q620 Motor Plants U.S.C.G. Merchant Marine Exam DDE-Unlimited HP Illustrations: 34 42. After a main diesel engine on your river push boat has experienced a safety shutdown due to

excessive crankcase pressure, why is it important to wait 2 hours before opening the crankcase to investigate the cause of the trip?

o (A) Opening the crankcase before 2 hours has elapsed may result in the engine spontaneously restarting.

o (B) Opening the crankcase before 2 hours has elapsed may result in crankshaft rotation. • (C) Opening the crankcase before 2 hours has elapsed may result in a crankcase explosion. o (D) Opening the crankcase before 2 hours has elapsed may result in excessively rapid cooling.


43. A main propulsion diesel engine on your ship docking tug has experienced a safety shutdown due to high lubricating oil temperature. What is the appropriate response?

o (A) Allow the engine to cool off for two minutes, then restart and monitor the lubricating oil temperature to verify the cause of the shutdown.

o (B) Immediately perform the engine inspections to determine the cause of the high oil temperature safety shutdown.

• (C) Allow 2 hours for the engine to cool down before attempting to inspect the engine and correct the cause of the trip before attempting to restart the engine.

o (D) Immediately restart the engine, and monitor the oil temperature to verify the cause of the shutdown.


44. While warming up the main engines on your harbor tug while tied up at your own pier, one of the main engines suddenly sounds the low lube oil pressure alarm. What is the appropriate initial response?

• (A) Immediately shutdown the engine, then investigate the cause for the low pressure alarm. o (B) Reduce the load and speed on the engine and continue to monitor the oil pressure. o (C) Monitor closely oil pressures, temperatures, and levels while continuing to run the engine. o (D) Immediately add make-up oil or service lube oil coolers, strainers, and filters, as appropriate.


45. You are serving as a designated duty engineer onboard a harbor tug equipped with main propulsion diesel engines of the type shown in the illustration. What scavenging flow pattern is used in this engine type? Illustration MO-0227

• (A) Uniflow o (B) Return-flow o (C) Loop o (D) Cross-flow



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Q620 Motor Plants U.S.C.G. Merchant Marine Exam DDE-Unlimited HP Illustrations: 34 46. You are assigned to a salvage tug fitted with main propulsion diesel engines of the type shown in the

illustration. If the engine's crankshaft is turning at 720 rpm, what will be the rotational speed of the two camshafts? Illustration MO-0006

• (A) 360 rpm o (B) 720 rpm o (C) 1440 rpm o (D) Not enough information is given to determine camshaft rpm.


47. The ship-docking tug to which you are assigned has main engines fitted with injectors similar to those shown in the illustration. What statement is true concerning the operating principle of this type of injector? Illustration MO-0151

• (A) The fuel pressure within the annulus is a needle valve opening force, the compression load on the spring is a needle valve closing force.

o (B) The fuel pressure within the annulus is a needle valve closing force, the compression load on the spring is a needle valve opening force.

o (C) The fuel pressure within the annulus and the compression load on the spring are both needle valve opening forces.

o (D) The fuel pressure within the annulus and the compression load on the spring are both needle valve closing forces.


48. The harbor tug to which you are assigned has a main engine fuel system as shown in the illustration. Besides preventing the attached fuel oil pump and the hand priming fuel oil pump from discharging through the other, what other purpose do the anti-flood check valves serve? Illustration MO-0152

o (A) They prevent backflow of fuel from the engine to the day tank when the engine is shut down and when the day tank is located above the engine.

• (B) They prevent backflow of fuel from the engine to the day tank when the engine is shut down and when the day tank is located below the engine.

o (C) They prevent backflow of fuel from the engine to the day tank when the engine is running and when the day tank is located above the engine.

o (D) They prevent backflow of fuel from the engine to the day tank when the engine is running and when the day tank is located below the engine.


49. The deck winch drive engine onboard your salvage tug uses a lubricating oil filtration scheme as shown in the illustration. What type of filtration system is illustrated? Illustration MO-0182

o (A) Shunt filtration o (B) Sump filtration o (C) Full-flow filtration • (D) Bypass filtration



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Q620 Motor Plants U.S.C.G. Merchant Marine Exam DDE-Unlimited HP Illustrations: 34 50. The main propulsion engines onboard your tractor tug use a lubricating oil system as shown in the

illustration. What item number represents the lubricating oil filter? Illustration MO-0183

o (A) 2 • (B) 5 o (C) 10 o (D) 12


51. The main propulsion diesel engines fitted on your salvage tug are started with compressed air using the system illustrated. What is the starting method used with this system? Illustration MO-0199

o (A) Hydraulic cranking motor(s) with air over hydraulics o (B) Direct air admission with air start distributor o (C) Direct air admission with cam actuated air start valves. • (D) Air cranking motor(s)


52. The river push boat to which you are assigned is fitted with generator engines as partly shown in the illustration. What statement is true concerning the cylinders? Illustration MO-0163

• (A) The cylinder liners are of the wet type and are replaceable inserts. o (B) The cylinder walls are integral (non-replaceable) to the cylinder block. o (C) The cylinder liners are of the dry type and are replaceable inserts. o (D) The cylinder liners are of the jacketed type and are replaceable inserts.


53. The ship-docking tug to which you are assigned is fitted with auxiliary diesel engines of the type shown in the illustration. In terms of valve operating gear and cylinder liner type, what statement is true? Illustration MO-0006

o (A) This is a pushrod operated overhead valve engine with jacketed cylinder liners. o (B) This is an overhead cam engine with wet cylinder liners. • (C) This is a pushrod operated overhead valve engine with wet cylinder liners. o (D) This is an overhead cam engine with jacketed cylinder liners.



8/18/2021


54. The ship-docking tug to which you are assigned is fitted with main propulsion diesel engines of the type shown in the illustration. In terms of valve operating gear, cylinder liner type, and connecting rod type, what statement is true? Illustration MO-0192

o (A) This is an overhead cam engine, with wet cylinder liners and conventional connecting rods. o (B) This is an overhead cam engine, with jacketed cylinder liners and marine-type connecting

rods. • (C) This is a pushrod operated overhead valve engine, with wet cylinder liners and conventional

connecting rods. o (D) This is a pushrod operated overhead valve engine, with jacketed cylinder liners and

articulated connecting rods.


55. The river push boat to which you are assigned has diesel generators fitted with intake and exhaust systems as shown in the illustration. What does the component labeled "3" represent? Illustration MO-0176

o (A) Exhaust manifold o (B) Wet muffler o (C) Charge air manifold • (D) Charge air cooler


56. The harbor tug to which you are assigned has main engines fitted with intake and exhaust systems as shown in the illustration. What type of turbo-charging configuration is used? Illustration MO-0076

o (A) Constant pressure turbo-charging. o (B) Boost-controlled turbo-charging. • (C) Pulse turbo-charging. o (D) 2-stage turbo-charging.


57. The fresh water cooling systems serving the main engines of the towing vessel to which you are assigned are arranged as shown in the illustration. What statement best describes the arrangement of the fresh water keel cooler shown in the system diagram? Illustration MO-0138

o (A) The keel cooler is mounted on the inside of the hull above the water line. o (B) The keel cooler is mounted on the outside of the hull above the water line. • (C) The keel cooler is mounted on the outside of the hull below the water line. o (D) The keel cooler is mounted on the inside of the hull below the water line.



8/18/2021

Q620 Motor Plants U.S.C.G. Merchant Marine Exam DDE-Unlimited HP Illustrations: 34 58. The winch drive engine on the harbor tug to which you are assigned is fitted with a Roots-type

blower as shown in the illustration. What statement is true concerning this blower? Illustration MO-0082

o (A) Rotor "1" turns clockwise, and rotor "2" turns counter-clockwise. Area "3" is the discharge passage, and area "4" is the suction passage.

• (B) Rotor "1" turns counter-clockwise, and rotor "2" turns clockwise. Area "3" is the discharge passage, and area "4" is the suction passage.

o (C) Rotor "1" turns counter-clockwise, and rotor "2" turns clockwise. Area "3" is the suction passage, and area "4" is the discharge passage.

o (D) Rotor "1" turns clockwise, and rotor "2" turns counter-clockwise. Area "3" is the suction passage, and area "4" is the discharge passage.


59. The ship-docking tug to which you are assigned is fitted with main propulsion engines driving through pneumatic airflex clutches as shown in the illustration. What statement is true concerning this type of clutch? Illustration MO-0141

o (A) The clutch is a constricting type clutch and constricts to engage against the clutch gland when inflated.

o (B) The clutch is an expanding type clutch and expands to engage against the clutch drum when inflated.

o (C) The clutch is an expanding type clutch and expands to engage against the clutch gland when inflated.

• (D) The clutch is a constricting type clutch and constricts to engage against the clutch drum when inflated.


60. Suppose one of the overhead camshafts on the V-type main propulsion diesel engines on your tug are fitted on the forward end with the device shown in the illustration. In addition to serving as a counterweight, what other function does the device serve? Illustration MO-0101

o (A) Overload sensor o (B) Torsional vibration damper o (C) Harmonic balancer • (D) Overspeed trip


61. The steam generating plant on your articulated tug-barge unit is of the forced-circulation type. Which figure of the illustration represents a steam generator or boiler of this type? Illustration MO-0197

o (A) 1 o (B) 2 • (C) 3 o (D) 4



8/18/2021

Q620 Motor Plants U.S.C.G. Merchant Marine Exam DDE-Unlimited HP Illustrations: 34 62. Diesel engine closed, re-circulating cooling water systems are particularly prone to cavitation

corrosion/erosion. Which of the listed cooling system/engine components has surfaces in contact with the coolant that are most susceptible to this type of corrosion and erosion?

o (A) Engine exhaust cooling water jackets. o (B) Cylinder cooling water jackets. o (C) Cylinder head cooling water passages. • (D) Wet-type cylinder liners.


63. What statement is true concerning diesel engines, such as those used for main propulsion and auxiliary power on tugboats?

o (A) Diesel engines are reciprocating, internal combustion engines using an electric spark to achieve ignition.

o (B) Diesel engines are rotary, internal combustion engines using the heat of compression to achieve ignition.

• (C) Diesel engines are reciprocating, internal combustion engines using the heat of compression to achieve ignition.

o (D) Diesel engines are reciprocating, external combustion engines using the heat of compression to achieve ignition.


64. Suppose the diesel generator set drive engines on your ocean-going tug are fitted with pressure-compensated governors as shown in the illustration. What is the significance of the oil inlet connection with this particular governor? Illustration MO-0219

• (A) The governor uses engine oil as a lubricant and a hydraulic power medium. o (B) The governor uses variable engine lube oil pressure to sense engine speed. o (C) The governor uses low engine lube oil pressure to trigger an alarm. o (D) The governor uses low engine lube oil pressure to execute a safety shutdown.


65. You are preparing to change the oil of the speed control governor on one of the main propulsion diesel engines on your towing vessel. What statement is true concerning the draining and flushing procedures?

o (A) The governor oil should be drained while the oil is cold and the governor should be flushed with the heaviest grade of the same type of oil.

• (B) The governor oil should be drained while the oil is hot and the governor should be flushed with the lightest grade of the same type of oil.

o (C) The governor oil should be drained while the oil is hot and the governor should be flushed with the heaviest grade of the same type of oil.

o (D) The governor oil should be drained while the oil is cold and the governor should be flushed with the lightest grade of the same type of oil.



8/18/2021

Q620 Motor Plants U.S.C.G. Merchant Marine Exam DDE-Unlimited HP Illustrations: 34 66. Suppose the main propulsion diesel engines on your river pushboat are fitted with pressure-

compensated governors as shown in the illustration. What function does the engine lube oil pressure connection provide? Illustration MO-0156

o (A) It is used as a governor lubricant and as a hydraulic power medium for the power cylinder. o (B) It is used solely for the purpose of achieving engine shutdown on low engine lube oil

pressure. o (C) It is used solely for the purpose of activating an alarm on low engine lube oil pressure. • (D) It is used for both activating an alarm and achieving engine shutdown on low engine lube oil

pressure.


67. The pneumatic propulsion control system used on your river pushboat uses a diaphragm-operated relay valve as shown in the illustration. Periodically, the valve is to be disassembled for cleaning and inspection. What statement best describes the proper technique? Illustration MO-0052

o (A) Rubber parts such as the diaphragm and metal parts such as the valve discs and seats should all be washed with soap and water.

o (B) Rubber parts such as the diaphragm should be cleaned with non-flammable solvent, and metal parts such as the valve discs and seats should be washed with soap and water.

• (C) Rubber parts such as the diaphragm should be washed with soap and water, and metal parts such as the valve discs and seats should be cleaned with non-flammable solvent.

o (D) Rubber parts such as the diaphragm and metal parts such as the valve discs and seats should all be cleaned with non-flammable solvent.


68. The salvage tug to which you are assigned is fitted with a totally pneumatic propulsion control system as shown in the illustration. If the astern clutch fails to engage from all control locations, but the ahead clutch properly engages from all control locations, which of the following system faults best accounts for these symptoms? Illustration MO-0168

o (A) The control lever at the pneumatic remote control station has a blocked astern clutch engagement pilot port.

o (B) The control lever at the engine room control station has a blocked astern clutch engagement pilot port.

o (C) The ahead clutch engagement pilot air tubing has separated from the clutch actuator 4-way control valve at the clutch control panel.

• (D) The astern clutch engagement pilot air tubing has separated from the clutch actuator 4-way control valve at the clutch control panel.



8/18/2021


69. Suppose the generator set drive engines on your ship docking tug are fitted with hydraulic isochronous governors such as shown in the illustration. How is the speed set point conveyed from the generator control panel on the main switchboard conveyed to the governor fitted on the diesel engine? Illustration MO-0160

o (A) Hydraulically via tubing connections o (B) Pneumatically via tubing connections • (C) Electrically via wire connections o (D) Mechanically via cable connections


70. An auxiliary plant on board a mobile offshore drilling unit that is invariably automated is the compressed air plant. Suppose the air compressors of such a plant are configured for lead-lag operation as shown in the illustration. If the sequence selector station is configured for #1 compressor to be the lead compressor and the #2 compressor to be the lag compressor, what statement is true? Illustration GS-0188

o (A) #2 compressor would be the "duty" compressor, cycling off and on when the system demand for compressed air is light, and #1 compressor would be the "standby" compressor, cycling off and on only when the system demand for compressed air is heavy. As a consequence, #1 compressor will accumulate more running hours than #2 compressor.

o (B) #2 compressor would be the "duty" compressor, cycling off and on when the system demand for compressed air is light, and #1 compressor would be the "standby" compressor, cycling off and on only when the system demand for compressed air is heavy. As a consequence, #2 compressor will accumulate more running hours than #1 compressor.

• (C) #1 compressor would be the "duty" compressor, cycling off and on when the system demand for compressed air is light, and #2 compressor would be the "standby" compressor, cycling off and on only when the system demand for compressed air is heavy. As a consequence, #1 compressor will accumulate more running hours than #2 compressor.

o (D) #1 compressor would be the "duty" compressor, cycling off and on when the system demand for compressed air is light, and #2 compressor would be the "standby" compressor, cycling off and on only when the system demand for compressed air is heavy. As a consequence, #2 compressor will accumulate more running hours than #1 compressor.



8/18/2021

National Maritime Center Serving Our Nation’s Mariners

5/9/2019

GS-0188

Adapted for testing purposes only from McGEORGE, Marine Auxiliary Machinery, 7th edition

Copyright © 1995 by Butterworth-Heinemann

Further reproduction prohibited without permission of 56 Q620 Motor Plants

National Maritime Center

Serving Our Nation’s Mariners

10/17/2018

MO-0006

Adapted for testing purposes only from WILBU R, Pounder's Marine Diesel Engines, Sixth edition

Copyright © 1986 by Butterworth's Publishers

Further reproduction prohibited without permission of 56 Q620 Motor Plants



10/19/2018

Adapted for testing purposes only from CALDER, Marine Diesel Engines

Maintenance, Troubleshooting, and Repair

Copyright © 1992 by International Marine, a Division of The McGraw-Hill Companies

Further reproduction prohibited without permission

MO-0051




10/19/2018

Adapted for testing purposes only from WABTEC H5 Relayair Valve, Operation and Maintenance Instruction

Copyright © 2000 WABCO Locomotive Products.


MO-0052




10/19/2018

Adapted for testing purposes only from GUNTHER, Lubrication

Copyright © 1971 by Raymond C. Gunther


MO-0057




10/19/2018 Adapted for testing purposes only


MO-0076




10/19/2018

Adapted for testing purposes only from KATES/LUCK, Diesel and High Compression Gas Engines, 3rd edition

Copyright © 1974 by American Technical Society


MO-0082




10/19/2018

Adapted for testing purposes only from STINSON, Diesel Engineering Handbook, 12th Edition

Copyright © 1981 Business Journals, Inc.


MO-0089




10/19/2018

Adapted for testing purposes only from MAGNETROL, Installation, Maintenance, Operating Instructions for

Models W126, W127, W251, W252, W291

Copyright © Magnetrol division of Schaub Engineering Co.


MO-0093




10/22/2018

Adapted for testing purposes only from Replacement Parts Catalog No. 302, Diesel Engine Model 645 for Power

Generation and Marine Propulsion

Copyright © 1989 Electro-Motive Division, General Motors Corporation


MO-0101




10/24/2018

Adapted for testing purposes only from Marine Propulsion Unit Operating Manual

Copyright © 1988 by Electro-Motive Division, General Motors Corporation


MO-0137 EMD Engine Fresh Water

Cooling System with Heat Exchanger




10/24/2018




MO-0138 EMD Engine Fresh Water

Cooling System with Keel Cooler




10/25/2018

Adapted for testing purposes only from Engineman 3

NAVEDTRA 14331


MO-0141 Pneumatic Airflex Clutch Operation




10/25/2018

Adapted for testing purposes only from NORMAN Diesel Technology: Fundamentals, Service, Repair

Copyright © 2007 by the Goodheart-Wilcox Company, Inc.


MO-0144 Detroit Diesel 71 Series Engine Unit Injector




10/25/2018




MO-0145 Plunger Type Fuel Injection Pump

with Port and Helix Metering




10/25/2018

Adapted for testing purposes only from NORMAN, Diesel Technology: Fundamentals, Service, Repair



MO-0151




10/25/2018




MO-0152




10/25/2018

Adapted for testing purposes only from 645E7B Turbocharged Marine Engine/Systems, 1st Edition

Copyright © 1980 Electro-Motive Division of General Motors


MO-0156 Woodward Type PGA Governor

Schematic Diagram




10/25/2018

Adapted for testing purposes only from PSG Governor with Aluminum Case

Installation and Operation Manual 37013 (Revision M)

Copyright © 1975 by Woodward


MO-0160 Woodward Type PSG Governor




10/25/2018

Adapted for testing purposes only from TOBOLDT, Diesel Fundamentals, Service, Repair

Copyright © 1973 by the Goodheart-Willcox Co., Inc.

Further reproduction prohibited without permission.

MO-0163




10/25/2018

Adapted for testing purposes only from Falk Marine Reduction Drives,

Installation, Operation and Maintenance Manual

Copyright © 1976 Faulk


MO-0168 Pneumatic Propulsion Control System




10/25/2018

Adapted for testing purposes only from 645E7B Turbocharged Marine Engine/Systems, 1st Edition

Copyright © 1980 by Electro-Motive Division of General Motors


MO-0171 EMD 645 Overspeed and Manual Trips




10/25/2018

Adapted for testing purposes only from KATES, Diesel and High Compression Gas Engines, 3rd Edition

Copyright © 1974 by American Technical Society


MO-0180




10/25/2018




MO-0182 Simplified Lube Oil Filtration System




10/25/2018

Adapted for testing purposes only from ALCO 251 Instruction Manual

Copyright © ALCO


MO-0192 ALCO 251 Series Engine




10/26/2018

Adapted for testing purposes only from 645/710 Marine Propulsion Unit Operating Manual



MO-0199 EMD Air Start System




10/26/2018

Adapted for testing purposes only from 645/710 Marine Propulsion Unit Operating Manual



MO-0200 EMD Air Start System Piping at Engine




10/26/2018

Adapted for testing purposes only


MO-0209 Freezing Point of Coolant as a

Function of Glycol Concentration




5/14/2019

Adapted for testing purposes only from WOODWARD, PSG Governor with Aluminum Case

Operation and Maintenance Manual

Copyright © 1975 by Woodward Governor Company


MO-0219




1/9/2019

Adapted for testing purposes only from EMD 645E9 Turbocharged Engine Maintenance Manual

Copyright © 1973 Electro-Motive Division, General Motors


MO-0227


USCG Merchant Marine Exam DDE - National Maritime Center

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Transcript of USCG Merchant Marine Exam DDE - National Maritime Center